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Ehunt

AR Pistol over-gassing?

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So, I built an AR Pistol with a PSA 8.5" Gov profile Barrel (link at bottom); it is Semi-Auto only. It does function fine, but I notice that my brass ejects at the 1:30 to 2 o'clock position. I have read several articles stating that they should eject anywhere between the 3 o'clock to 4:30 positions, or close to that. I am currently using an adjustable gas block and an H3 buffer with a SprinCo Red Extra Power Buffer Spring. Closing the gas block any further won't allow the carrier to lock open on a empty mag. I was thinking of purchasing an H3 buffer with a steel body, (some call this an H4 Buffer), to raise the buffer weight to about 6.8 ounces. Will this help, or is it even necessary?

Current Barrel: https://palmettostatearmory.com/psa-ar15-8-5-5-56-nato-1-7-pistol-length-nitride-barrel-5-56-nato-1-7-77932926.html

I've been thinking of switching to a Rainier Arms 1:8 twist barrel to fire 55 grain in tighter groupings: https://www.rainierarms.com/rainier-arms-match-223-wylde-750-gas-block-pistol-barrel-8-5/

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Is the ejection the only sign of overgas that you have?   Is your brass dented at all?   

If you have an adjustable gas block and the next setting down won't properly cycle the bolt, I'd lean towards your issue not be overgassing but something else.   

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9 hours ago, Capbyrd said:

Is the ejection the only sign of overgas that you have?   Is your brass dented at all?   

If you have an adjustable gas block and the next setting down won't properly cycle the bolt, I'd lean towards your issue not be overgassing but something else.   

I was playing around with it a bit today. The brass ejects now at about 2:30, I am guessing the cold is playing into that. The brass is not dented, but my extractor is sure chewing up the base. I did adjust my adjustable gas block down two clicks and this had no effect. I'll try again when I have more time.

Edited by Ehunt

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1 hour ago, Magiccarpetrides said:

honestly if its functioning well I sure wouldn't go any heavier than an H3...if the brass isn't dented I wouldn't be concerned at all.

Thanks. You're probably right. My H3 Buffer is about 5.5 ounces and I recently found another that is about 6.8 ounces. I figured this might put the ejecting brass right where I want it. But I definitely wouldn't go any heavier than this 6.8 ounce "H4" Buffer.

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I'd open the gas some more before swapping out the buffer.  I use Spikes ST-T2 buffer in my 10.5" SBR, and also have adjustable gas like you do, I just leave it a bit open so I can shoot 55gr and 62gr ammo without any changes and I've never had an issue with it.  I'm less worried about that unicorn of sweet spot, and just away from the spectrum of overgassed.

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5 minutes ago, btq96r said:

I'd open the gas some more before swapping out the buffer.  I use Spikes ST-T2 buffer in my 10.5" SBR, and also have adjustable gas like you do, I just leave it a bit open so I can shoot 55gr and 62gr ammo without any changes and I've never had an issue with it.  I'm less worried about that unicorn of sweet spot, and just away from the spectrum of overgassed.

Thanks, I'll have to test it out some more. I think I'm just going to change the barrel though. The 1:7 twist on this 5.56 NATO chambered barrel is just not holding the groupings I would like for it to with 55 grain ammo. The ejection problem might go away, who know with these things.

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Ehunt...what groupings are you getting?  and at what distance?  You might wanna go with a wylde chamber 1 in 8 if your wanting better accuracy with the 55's without losing too much range for the heavy rounds...a short barrel me personally I prefer the 1 in 7 because i'd rather use heavy bullets at closer ranges but that's just me...course I just shoot paper so it don't matter too much either way.

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On 1/26/2019 at 12:51 PM, Magiccarpetrides said:

Ehunt...what groupings are you getting?  and at what distance?  You might wanna go with a wylde chamber 1 in 8 if your wanting better accuracy with the 55's without losing too much range for the heavy rounds...a short barrel me personally I prefer the 1 in 7 because i'd rather use heavy bullets at closer ranges but that's just me...course I just shoot paper so it don't matter too much either way.

I agree with you Sir. With my current barrel, (8.5", 5.56 NATO chamber, 1:7 twist) the 55 grain has a pattern of 2" to 3" groupings at 25 yards. To me that is terrible. I found a barrel that I am considering to replace this one, it is a .223 Wylde barrel and I believe that it will preform much better. I could use heavier bullets for the 1:7 barrel, but they aren't as cheap as 55 grain.

I am also thinking that the ejection at 2 o'clock to 2:30 issue that I am having may also be due to the type of gas block I used. I used a Superlative Arms Adjustable Gas block. My AR-10 had cycling issues with a similar one and when I swapped it out with a Standard Gas Block, the issue resolved and the rifle functions perfectly now.

Superlative Arms' Adjustable Gas Blocks are designed with a port vent to "vent excess gas" from the system. In the case of my AR-10 it was venting too much gas and was causing short stroking. With my AR-15 Pistol, it may be allowing too much, not sure. But either way, I ordered a new adjustable gas block that is a closed system. We'll see how this works.

Edited by Ehunt
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On 1/29/2019 at 10:40 AM, Magiccarpetrides said:

have you tried some surplus 62gr (ala green tip)...its usually not very expensive...might be worth testing before making the switch.

I didn't try those exactly, but I did try heavier bullets (64gr SSA by Nosler, 69gr Match PPU, and 75gr Hornady Freedom) that I had bought on sale a while back that I keep for testing. The groupings did tighten up with the heavier bullets, as you would expect. The 75gr was about nickle sized groupings at 25 yards, unsupported. Very good, but it would be too expensive for me to only shoot 70+gr ammo out of just this gun. The barrel I am looking at is under $200 with a 1:8 twist and a .223 Wylde chamber. So that will allow me to get similar groupings with 55gr ammo (since my 18" 1:8 .223 Wylde rifle does just that), and save money in the long-run.

Edited by Ehunt
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Found the issue. The old barrel had an oversized gas port. Installed the new barrel today, adjusted the gas block and the ekection is right at the 3:30 position. Thanks for your input everyone.

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